Limitless Limitless Power Cut Out???

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Leejax01

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Arrma RC's
  1. Kraton 6s
Hey guys, I’ve been having an issue that’s been puzzling. It’s on a drag Limitless. I was running an XLX & a 6S system. Connectors are QS8 & 8 gauge wire where applicable. The car started to cut out on the hit with any battery other than a cheaper Lectron 6S pack. Thought it was the esc, so bought a newer XLX2.

Fast forward and I bought a 6S SMC 150C battery and it cuts out it again. Every hit this time like click work. Thinking maybe the motor or connectors, I bought a new motor, replaced the 8 gauge wire with new wire and new 8mm Castle connectors. Tried again and same thing. So at this point it’s a new esc, motor and 8 gauge wiring and even new QS8 connectors. It would cut out other than with my cheaper Lectron battery.

Last night we tried the car with the Lectron 6S battery and every hit it would cut out. Not matter starting power, punch settings, low voltage cut off is disabled. It shows 25.2V with .78V max ripple. At this point, there’s 2 different esc’s, 2 different motors, new wiring, countless esc & calibrations in different orientations that it’s getting ridiculous. Nothing is overpowered as it’s 6S on an 8S esc. Any help or direction is appreciated.
 
If it doesn't on one specific battery and also later does, battery seems to be the bottleneck.

It's not clear to me when it cuts out. Doesn't it even launch?
Drop in some datalogs? What amps are you pulling and how long? running high gearing?
 
What exact motor combo ? Kv? Gearing? When is it cutting out? More info! My guess is amperage overdraw. Plz b more specific

Figured it out. It was the receiver. Maybe a deadband issue or maybe something else. Not sure. I dropped in a Futaba receiver and radio. It pulls off the hit at the starting line like it should. It’s pulling about 590 amps and producing just over 12,000 watts

FC2067C9-4117-40E6-BFFE-5605CD18ABC4.jpeg
 
Figured it out. It was the receiver. Maybe a deadband issue or maybe something else. Not sure. I dropped in a Futaba receiver and radio. It pulls off the hit at the starting line like it should. It’s pulling about 590 amps and producing just over 12,000 watts

View attachment 147320
Those are some serious amps your pulling. That's pushing any battery to it's limit.
I would love to see your datalog throttle and amp curve
The futuba could just have a little more latency, compared to your other unmentioned radio/receiver making the amp peak a little less steep.
 
It was the Spectrum DX3 w SRS6110AT receiver. With the volts being 25.2 and a ripple of .8V, I knew it couldn’t have been amp draw also considering the XLX2 doesn’t have amps cut off, it can handle 600 plus amps plus, batteries never got warm and the SMC (6S 6400mah 150C w/ 8AWG) wire was the one cutting out. The Lectron 100C 6500mah wqould run all day every day no issues until the other day. Now when I tested with the SMC, which I could never previously under any condition, I’m seeing 18% to 28% gains in watts.
 
On pulling 590A on a 6400mah battery means your actually pulling 92C. Knowing that 100C/150C are marketing numbers, you are actually putting the batteries on their limits. As the XLX2 does not have a limit it's either the motor or battery that determines the limit. A motor will just burn when that happens, while a battery will indeed 'cut out' when it peaks above it's capability.

I speedrun, i don't drag, it's a different application. But it's your trigger finger that will determine your amp pull. When you pull too hard in low rpm's, amps will rocket. I don't know what distance you drag, but my senses are telling me you could be better of with a lower gearratio.

Preheating you batteries can help too. Above 40C/100C they preform significantly better
 
Did you see the ripple? When a sag happens, you’ll see ripple. It felt like a sharp cut out, like a misstep. After swapping out the receiver, it’s all around gains and I’m running the SMC battery I could never before.
 
Did you see the ripple? When a sag happens, you’ll see ripple. It felt like a sharp cut out, like a misstep. After swapping out the receiver, it’s all around gains and I’m running the SMC battery I could never before.
Ripple depends on caps quality/quantity and generally is a good indication of the power system stability. Low ripple is good, but not directly related to voltage sag.

At speed running there is always ridiculous sag, sag is normal. As i still don't know what distances you drag and not seen any datalog graphs or what sag you're facing during your drag, maybe we're comparing pears and apples, but i have certainly gathered enough data to know what I am talking about.
On my runs with lesser batteries where it actually hit the max amp capability and had 'cut outs', ripple stayed <1V and even sag wasn't extraordinary.

But yeah, if your problem is truly solved by your radio/receiver swap, it should be all fine now and you could ignore my ranting...
 
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